The present invention relates to a control system for a transmission which transmits torque from an engine to a drive axle of a vehicle, and which includes a power shift transmission and a reverser module.
Such transmissions are known to be used in agricultural utility vehicles, such as tractors. Shifting the power shift transmission causes a jerk which can be felt, since the multi-disk clutches of the power shift transmission are engaged or disengaged hydraulically without any modulation. This causes variations in the torque in the driveline of the vehicle and causes jerk-like vehicle movements which are unpleasant and which reduce the operating comfort.
Such jerking movements could be suppressed, for example, by controlling the engine to synchronize the output rotational speed of the engine with the new gear ratio of the power shift transmission. However, such a control of the engine could be costly to develop, since the generally complex control arrangement of the engine would then have to be further complicated by further functionality. Such a control may also result in higher fuel consumption of an internal combustion engine.
Published German patent DE 196 00 835 A1 shows a vehicle transmission which includes a power shift transmission, at least one multi-disk clutch and a further power shift transmission for shifting wider speed ranges. In order to suppress jerking motions during shift of the power shift transmission, a button is actuated manually by the operator, whereby the multi-disk clutch is disengaged for a predetermined time interval. In so far as this goes, this reduces or avoids the jerk resulting from shifting of the power shift transmission.
However, in the system of DE 196 00 835 A1, because the multi-disk clutch is completely disengaged, the connection between the engine and the drive axle is interrupted for the predetermined time interval, and this causes the vehicle stop or at least reduce its speed during operation under load or in uphill operation. This also results in a jerk which reduces operator comfort. Moreover, disengagement of the multi-disk clutch is possible only in the two upper gear ratios of the power shift gear box, since the vehicle has sufficient kinetic energy in these speed ranges so that the vehicle, as a rule, should not come to a complete stop.
It is desired to provide a control for transmission of this type which overcomes the aforementioned problems.